RRC ID 68534
Author Kitagawa K, Hiramatsu Y, Uchida C, Isobe T, Hattori T, Oda T, Shibata K, Nakamura S, Kikuchi A, Kitagawa M.
Title Fbw7 promotes ubiquitin-dependent degradation of c-Myb: involvement of GSK3-mediated phosphorylation of Thr-572 in mouse c-Myb.
Journal Oncogene
Abstract Expression of oncoprotein c-Myb oscillates during hematopoiesis and hematological malignancies. Its quantity is not only regulated through transcriptional control but also through the ubiquitin-proteasome pathway, accompanied by phosphorylation, although the mechanisms are poorly understood. In this report, we tried to identify an E3 ubiquitin ligase, which targets c-Myb for ubiquitin-dependent degradation. We found that an F-box protein, Fbw7, interacted with c-Myb, which is mutated in numerous cancers. Fbw7 facilitated ubiquitylation and degradation of c-Myb in intact cells. Moreover, depletion of Fbw7 by RNA interference delayed turnover and increased the abundance of c-Myb in myeloid leukemia cells concomitantly, and suppressed the transcriptional level of gamma-globin, which receives transcriptional repression from c-Myb. In addition, we analysed sites required for both ubiquitylation and degradation of c-Myb. We found that Thr-572 is critical for Fbw7-mediated ubiquitylation in mouse c-Myb using site-directed mutagenesis. Fbw7 recognized the phosphorylation of Thr-572, which was mediated by glycogen synthase kinase 3 (GSK3). In consequence, the c-Myb protein was markedly stabilized by the substitution of Thr-572 to Ala. These observations suggest that SCF(Fbw7) ubiquitin ligase regulates phosphorylation-dependent degradation of c-Myb protein.
Volume 28(25)
Pages 2393-405
Published 2009-6-25
DOI 10.1038/onc.2009.111
PII onc2009111
PMID 19421138
IF 7.971
Resource
Human and Animal Cells K562(RCB0027)